Question

Calculate the boiling point of a solution of 400.0 g of ethylene glycol (C₂H₆O₂) dissolved in 400.0 g of water. kf = 1.86°C/m and kb = 0.512°C/m. Use 100°C as the boiling point of water.

1) 70°C
2) 108°C
3) 8.3°C
4) 92°C
5) 130°C

Answer 1

To calculate the boiling point elevation, we first need to calculate the molality of the solution. The molality is calculated by dividing the moles of solute by the mass of the solvent, multiplied by 1000 to convert to molality. The boiling point elevation is then determined using the molality and the molal boiling point elevation constant, and can be added to the boiling point of pure water to find the boiling point of the solution.

Step-by-step explanation:

To calculate the boiling point of the solution, we need to determine the increase in boiling point caused by the presence of ethylene glycol. The boiling point elevation can be calculated using the equation: ΔT = kb * molality * i, where ΔT is the change in boiling point, kb is the molal boiling point elevation constant, molality is the molality of the solution, and i is the van't Hoff factor.

First, let's calculate the molality of the solution. The molality is the moles of solute (ethylene glycol) divided by the mass of the solvent (water), multiplied by 1000 to convert to molality:

Molality = (moles of ethylene glycol / mass of water) * 1000

The molar mass of ethylene glycol (C2H6O2) is 62.07 g/mol. Therefore, moles of ethylene glycol = 400.0 g / 62.07 g/mol. The mass of water is 400.0 g.

Using the given van't Hoff factor of 1 for ethylene glycol, we can now calculate the boiling point elevation:

ΔT = 0.512 °C/m * molality * 1

Finally, we can add the boiling point elevation to the boiling point of pure water to find the boiling point of the solution:

Boiling point of solution = 100 °C + ΔT